Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
using namespace std;

int n,m,num,x[1000007],y[1000007],head,tail,st[1000007];
char s[1007][1007];
bool vis[1007][1007];

inline void pd(int a,int b,int k){
	if((a<0)||(a>=n)||(b<0)||(b>=m)) return;
	if(vis[a][b]) return;
	if(s[a][b]=='#') return;
	++tail;
	x[tail]=a; y[tail]=b;
	st[tail]=k;
	vis[a][b]=1;
}

int main(){
	cin>>n>>m;
	for(int i=0;i<n;++i){
		scanf("%s",s[i]);
		for(int j=0;j<m;++j)
			if(s[i][j]=='.')
				++num;
	}
	if(s[0][0]=='#'||s[n-1][m-1]=='#') {printf("-1"); return 0;}
	vis[0][0]=1; ++tail; x[1]=0; y[1]=0; st[1]=1;
	int a,b;
	while(head<tail){
		++head;
		a=x[head]; b=y[head];
		if(a==n-1&&b==m-1){
			printf("%d",num-st[head]);
			return 0;
		}
		pd(a,b-1,st[head]+1);
		pd(a,b+1,st[head]+1);
		pd(a-1,b,st[head]+1);
		pd(a+1,b,st[head]+1);
	}
	printf("-1");
}